Armored conductor structure



Jan. 4, 1944. o. E. RASMUSSEN ARMORED CONDUCTOR STRUCTURE Filed March14, 1942 FIG. 2

l/VVENTOR 0. E RASMUSSEN ATTORNEY ous tape structure.

Patented Jan. 4, 1944 ARMORED CONDUCTOR STRUCTURE Osvald E; Rasmussen,Greenburg, N. Y., assignor to Bell Telephone Laboratories, Incorporated,New York, N. Y., a corporation of New York Application March 14, 1942,Serial No. 434,687

8 Claims.

This invention relates to armored conductor structures and moreparticularly to structures of this kind intended for burial directly inthe ground.

It is an object of the invention to provide an armored cable structurewhich is simple to produce, easy to lay and which will provide safeprotection against attacks by burrowing rodents.

The requirements of a cable of this type capable of answering theseobjects are as follows: Theconstruction should be as light as possibleto reduce cost of material and to simplify transportation and handling;the armoring should cover the insulated wires as completely as possibleto give adequate protection against attacks and, on the other hand,should permit bending of the cable on a comparatively small radiuswithout undue deformation of the armoring, thus permitting the use ofcomparatively small reels; the structure should be non-tangling andshould present a smooth surface to facilitate general handling.

In accordance with the invention, a cable structure of this kind isprovided which includes a single layer of armoring tape. The layer ofarmoring is formed of an armoring tape of suitable material and appliedlongitudinally of the conductor structure. The armoring forms acontinuous layer entirely enclosing the insulated conductor orconductors, except for narrow transverse openings cut in the material atfrequent intervals to permit bending of the armored structure withoutappreciable buckling of the tape material.

The armoring tape. may be more or less deflnitely sectionalized, thesections being separated by the said narrow openings, which are bridgedby small connecting portions to form a continu- The edge portions of thesections along the seam are made to overlap those of the opposite edgein a manner to interlock and thus prevent buckling of the tape materialalong the seam.

The openings in the body portion of the tape are wide enough to preventcrowding of the tape material on the inside of the bend without,

tures and reference will be made to the acconn panying drawing, inwhich:

Fig. 1 is a perspective view of an armored cable structure with partsbroken away to more clearly show the construction;

Fig. 2 is a plan view of the armoring tape used in the structure of Fig.1;

Fig. 3 is a perspective view of an armored cable structure similar tothat shown in Fig. 1 but using a modified construction of armoring tape;and

Fig. 4 is a plan view of the armoring tape used in the structure of Fig.3.

Referring now to Figs. 1 and 2, the cable structure comprises twoconductors l0 and II placed in parallel relation throughout thestructure and enclosed in insulating material l2, which may form asingle continuous body or may comprise two separate bodies ofinsulation, one about each conductor. The tape armoring surrounding theinsulation l2 comprises an armoring tape 2| of suitable material forprotection against gopher attacks. The structure may furtherincludeouter wrappings, such as at and 32 applied about the armoring tape.

This structure, containing two parallel conductors, thus issubstantially oval-shaped having two comparatively flat sides and tworounded sides or edges. Whereas the armoring tape shown in Fig. 1 isparticularly adapted for the oval structure, it may readily be adaptedfor structures of circular or other cross section. The armoring tape isshown more in detail in Fig. 2 in the form in which it is manufacturedbefore application to the cable structure.

The tape 2| presents a flat surface. In effect, it is subdivided intostrip portions 21 by narrow transverse openings 25, the strips beinginterconnected by means of short connecting portions 24 disposed in rowslongitudinal of the tape.

It will be noted in Fig. 2 that by the distribution of connectingportions 24 the tape has a series of edge sections 28 along each edge,separated by short narrow cuts and mutually displaced along the twoedges.

The tape 2| is applied longitudinally to one fiat side of the conductorstructure and is returned-bent about the two rounded edges to form aseam along the other flat side. As the tape is to partly underlie oneedge section and partly overlie the adjacent edge section along theopposite edge. In this manner an interlocked seam is provided which willpermit the overlapping portions along this scam to shift longitudinallywhen the armored cable is bent Without deformation of the tapematerially thus without unduly exposing the insulated conductors togopher attacks.

The tape material may be iron or steel or any other suitable compositionand may or may not have its surface treated, as by tinning orgalvanization. The material may be non-oxidizing and acid resistant tohave a long life in contact with earth and other substances present inthe ground.

The openings in the completed armoring should be not more than ,4; inchand should preferably average about inch in width. This is to permitlaying the cable in the ground with fairly sharp curves or bends withoutunduly exposing the insulation to gopher attacks when the openings arewidened on the outside of the bend. On the other hand, openings of thiswidth will also prevent crowding of the tape material on the inside ofthe bend, when the cable is laid or when it is reeled, so that thearmoring tape will not be unduly deformed and forced out of position,thereby exposing the insulation to gopher attacks.

It has been found that by means of these narrow transverse openings thetape portions forming the main surface of the armoring are free to shiftslightly along the cable surface either to widen the openings or toclose them up when the cable is bent and therefore the tendency tobuckle and expose the underlying cable insulation is absent when smallcables are wound on their flat sides on reels as small as 12 inches indiameter.

It has also been found that the introduction of narrow transverseopenings in the tape material and particularly of the helicaldistribution of the openings with a comparatively small pitch is greatlyeffective in reducing the usual stiffness of armored cables of thisgeneral type and in easing the handling thereof, both in factory andfield.

The modified cable structure shown in Fig. 3 is similar to that shown inFig. 1 but difiers from that in Fig. l by having an armoring tape 2|, asshown in Fig. 4. The armoring tape of structure 2! has its transversestrip portions 2'! dis-- posed at an oblique angle with respect to thecenter line due to the cutting at an oblique angle of the transverseopenings 25'. As appears from Fig. 3, each strip portion! is appliedabout the cable along a helix with a pitch such that one end of eachstrip becomes aligned with an opposing end of the adjacent strip alongthe seam to. in effect, form a substantially continuous helical tapeabout the cable and thu insure a high degree of flexibility. Thearrangement at the same time provides for the halfway displacement ofthe edge sections 28' along one edge relative to those along theopposing edge and thus permits an interleaving of the edge sectionssimilar to that secured by the tape shown in Fig. 1.

The tape construction shown in Fig. 4 serves as an example in showingthat the underlying corner 28' of each edge section may be blunted sothat it will not tend to cut into the insulation when the cable is bentover the flat side. The

same eil'ect may be secured by rounding the inside comer.

The outer wrappings II and 32 may be of fibrous material, such as paper,and are helically applied in tape form. The wrappings may be impregnatedor coated with any suitable substance to retard their deterioration.

Cables of the type described above may be used for supplying electriclight andpower or for communication purposes. Since they areparticularly adapted for use in rural areas the distances over whichsuch cables will be used are usually quite considerable. It is therefore01' great importance that the cost of manufacture and the cost oftransportation and laying be as low as possible.

The self-contained cable structure described above is thereforepreferable over cables made in conduits, since the cable may be ploweddown in a fast continuou process from reel 0! rev.- s'onable size. Thedescribed structure is' readily unbent from the reel and laid in sharpcurves without danger of the tape buckling and unduly opening along theseam. With one Or. two wrappings outside the armoring there is no dangerof tangling or catching as the cable leaves the reel and the cable mayalso readily be manipulated by hand wtihout danger of injury.

The described structure lends itself particularly to fast manufacturingas compared with cables having helically armored tapes, since thelongitudinal tape may be applied and locked in position as fast as theinsulated conductor structure can be produced.

Due to the fact that the finished armoring is in effect broken up into alarge number of small shields or strips separated by narrow openings adegree of flexibility may be secured which is at least as high as withhelically applied armoring tape.

The absence of buckling of the armoring is especially important inassuring definite protection against gopher attacks and is attained bythe introduction of the transverse openings in the material which willpermit a slight shifting of the armoring material relatively to theinsulation, particularly on the inside of the bend, when the cable isbent. The armored cable may therefore be wound on reasonably small reelswithout danger of opening up along the seam. Thus storage,transportation and laying is greatly facilitated.

It should be understood that the cable may include more than twoconductors arranged in a single layer and may contain more than one suchlayer of a plurality of conductors. A single conductor cable, circularor flat, is also contemplated within the scope of the invention. The twoor" more conductors may be twisted together or otherwise intertwined anda concentric arrangement is also contemplated within the scope of theinvention.

What is claimed is:

1. A long insulated conductor, an armoring tape forming a generallycontinuous layer enveloping said conductor, the edges of the armoringtape having transverse cuts at frequent intervals to form a series ofedge sections, said edge sections on opposite edges being relativelydisplaced longitudinally and being long enough to overlap alternatelywith the displaced edge sections along the opposite sides of the seam.

2. A long insulated conductor, an armorlng tape placed tightly about andlongitudinally of said insulated conductor and forming a generallycontinuous layer enveloping said conductor, the edges of the armoringtape forming a seam parallel with said conductor and having transversecuts at frequent intervals to form a series of edge sections, said edgesections on opposite sides of said seam being relatively displacedlongitudinally and being long enough to overlap with the displaced edgesections along the opposite side of said seam, each of said edgesections underlying one and overlying another of said edge sections onthe opposite side of said seam. 4

3. A long insulated conductor, an armoring tape placed tightly about andlongitudinally of said insulated conductor and forming a generallycontinuous layer enveloping said conductor, said tape armoring formingsaid generally continuous layer with a longitudinal seam and having aseries of edge sections disposed along each side of said seam andalternately interleaved with the edge sections from the opposite sidesof said seam.

4. A long insulated conductor, an armoring tape placed tightly about andlongitudinally of said insulated conductor and forming a singlegenerally continuous layer enveloping said conductor, said armoring tapehaving a body portion running longitudinally of said conductor andhaving edge sections extending transversely of said conductor from theopposite sides of said body portion, said edge sections from each side.

of said body portion being spaced apart and disposed to form a lockingseam together with edge sections along the. opposite side of said seam,each of said edge sections partly overlying and partly underlying theopposite side of the seam.

5. A long, substantially oval-shaped, armored conductor structure havingtwo opposed comparatively fiat sides and two opposed rounded sides andbeing particularly adapted for bending over said flat sides on a smallradius, including a plurality of insulated conductors and tape armoringclosely surrounding said insulated conductors for protection againstattacks by rodents, said tape armoring comprising an armoring tapeforming a single continuous layer enveloping said plurality ofconductors and having a seam disposed along one of said fiat sides, saidarmoring tape having a continuous body portion and a series ofedgeprojections along each edge of said tape, said projections onopposite sides of said seam being at frequent intervals, the cuts alongone edge being displaced longitudinally relatively to those along theother edge and being astride the opposed edge between cuts.

7. A long, substantially oval-shaped armored conductor structure havingtwo opposed comparatively fiat sides and two opposed rounded sides andbeing particularly adapted for bending over said fiat sides on a smallradius, including a plurality of insulated conductors and tape armoringclosely surrounding said insulated conductors for protection againstattacks by rodents, said tape armoring comprising an armoring tapeforming a single continuous layer enveloping said plurality ofconductors and having a seam disposed along one of said fiat sides, saidarmoring tape having a continuous body portion with a series of edgeprojections on each side extending across said seam to interlock thetape edges, each of said edge projections overlying one and underlyinganother of the projections on the opposite side of said seam.

8. A long, substantially oval-shaped, armored conductor structure havingtwo opposed comparatively flat sides and two opposed rounded sides andbeing particularly adapted for bending over said flat sides on a smallradius, including a plurality of insulated conductors and tape armoringclosely surrounding said insulated conductors fon protection againstattacks by rodents, said tape armoring comprising an armoring tapeforming a single continuous layer enveloping said plurality ofconductors and having a seam disposed along one of said flat sides, saidarmoring tape comprising a series of transverse strip portions and shortconnecting portions between said strip portions for forming a continuoustape structure, each of said strip portions being long enough to overlapacross said seam and being disposed along a helix about said conductorstructure to have one of its ends partly overlie its other end andpartly underlie the end of an adjacent strip portion along said seam.

OSVALD E. RASMUSSEN.

